This invention relates to spread roller systems usable in photographic products and, more particularly, to adjustable spread roller systems usable in a photographic apparatus of the instant type.
In photographic apparatus of the instant type, there is provided a spread roller system which typically includes a pair of rotatable pressure rollers. In operation, these rollers serve to release, advance and spread a liquid photographic reagant in a film unit as the latter passes therebetween. These rollers are biased towards each other and have a predetermined minimum gap therebetween. It is critical in such systems to have the minimum gap accurately set because the quality of the final image depends on the thickness of the processing fluid layer.
Commonly-assigned U.S. Pat. No. 2,686,716, issued to E. H. Land, describes two approaches for establishing the predetermined minimum gap. One approach establishes the gap through appropriately spaced apart openings formed in bearing plates rotatably supporting the rollers. The other more commonly used approach sets the gap by a pair of longitudinally spaced metallic collars on one roller which contact the periphery of the other roller. In this latter approach, each collar has a height on the order of the thickness desired for the layer of processing fluid to be spread. Such spread roller systems serve satisfactorily for the purposes intended.
However, it is desirable to switch between different kinds of film units. This is a practical difficulty insofar as the different types of film units, for example, black-and-white as opposed to color, require different processing fluid thicknesses. Obviously, such a requirement necessitates a change in the gap whenever it is desired to use a film unit requiring different thicknesses. For instance, to change from one film unit to another in a large format camera (e.g., 20".times.24") requires replacement of the long roller carrying the gap spacing collars. Clearly, this causes a significant expenditure of time and is rather cumbersome. Obviously, it takes away from the photographer's time for photographic purposes. Consequently, different spread roller systems of the type having appropriately dimensioned collars would require replacement of the rollers for each change. Clearly, such kinds of changes prove burdensome and time-consuming.
Proposals have been put forth for adjusting the thicknesses of the processing fluid layer. One approach, disclosed in commonly-assigned U.S. Pat. No. 3,335,652, achieves different processing fluid thicknesses by adjusting the compressive forces of the spring system biasing the rollers together. Another approach for adjusting this gap is set forth in commonly-assigned U.S. Pat. No. 3,882,518. This latter patent discloses manually operated means for uniformly or differentially adjusting the spacing separating the cooperating spreading rollers and/or the magnitude of the biasing force applied by the rollers. With the foregoing proposed systems there are, however, no convenient, rapid and relatively reliable ways of accurately presetting the gap spacing.